Field of the Invention

The present invention relates to an umbilical handling system and in particular the design and arrangement of sheaves and roller guides for supporting an umbilical.

Background to the Invention

In offshore drilling environments it is necessary to supply hydraulic signals and fluids to the wellhead and the standard practice is to use a hydraulic sub-sea control umbilical hose for the purpose of the workover control where workover operations are performed on a sub-sea wellhead using a workover riser and/or for blow out preventer control and actuation.

Typically umbilicals are stored, deployed and recovered from a hydraulic or air powered reel on the topside, for example, on a ship or other offshore installation. Umbilicals are deployed, operated and recovered via umbilical handling systems that generally comprise a support structure for holding a reeled umbilical and a plurality of rollers and/or sheaves which define the route along which an umbilical is deployed or recovered along. A heave compensation system will also generally be included in an umbilical handling system.

Umbilicals as they pass through conventional umbilical handling systems are subjected to various tensile and bending loads during deployment, operation and recovery as they are paid off and paid on to the reel support structure over various sheaves, roller guides and compensation systems.

To satisfy demand for oil there have been moves recently to develop and recover oil reserves from deeper waters which has resulted in workover and blowout preventer umbilicals being significantly longer than previous designs of umbilical due to the increased distance from the topside to the wellhead. In view of the increased costs associated with deepwater oil recovery it is essential that umbilicals and their associated umbilical handling systems maintain their functionality and reliability. Furthermore umbilicals are now expected to be more reliable, to have longer design lives and operational lives to optimise the value or reusability of such assets. This has resulted in fatigue levels being higher which has resulted in the designs of umbilicals changing to meet these demands. With such increasing water depths, greater demands from heave compensation systems the loads imposed on umbilicals are now higher and bending fatigue is greater.

Conventionally there are used typically V shaped sheaves or rollers - see for example the roller design shown in figure 1 and are formed and arranged with an open structure such that an umbilical passing thereover will be centralised on the roller. Umbilicals typically operate at tensions in the region of 5 to 20kN and at the points where the umbilical makes contact with the surface of the roller, the operating tensile loads within the umbilical are supported and absorbed. With such conventional rollers these contact loads act on small areas between the umbilical and the roller resulting in high contact pressures resulting in high levels of deformation and ovalisation of the umbilical as it attempts to resist these loads. It will be understood that as the umbilical passes through the multiple roller sheaves it makes repeated intermittent contact with the rollers which results in differing deformation at any given location along an umbilical.

It has been found that the repeated/cyclic deformation of the umbilical outer jacket translates and passes into the individual hoses within the umbilical core. Typically the hoses are high pressure thermoplastic hoses which have hose reinforcement layers. The contact forces and aforementioned ovalisation damage the hose pressure containment reinforcement layers due to lateral cyclic compression forces and fibre abrasion between adjacent fibres and the polymers of the pipe core tube and/or the outer jacket occurs due to the relative movement whilst under tensile and lateral compressive loads. This ovalisation and associated damage can result in the hose pressure containment capacity reducing significantly from up to four times that of the working pressure of the hose to levels around actual working pressure such that hose failure may occur in the field during operation when significant operational umbilical life has been consumed. It has been found that this ovalisation and gradual degradation is not linear but exponentially more aggressive at the start of the operational life of an umbilical.

It is the object of the present invention to provide an improved umbilical handling system and apparatus which avoids or minimises one or more of the aforementioned disadvantages of current designs. Description of the Invention

The present invention provides an umbilical handling system comprising an umbilical support reel; an umbilical feed/recovery path defined by a support structure formed and arranged for supporting a plurality of umbilical support rollers; characterised in that said rollers have a 'U' shaped groove profile and dimension formed and arranged to conform to the cross-sectional profile and dimensions of an umbilical in use of the handling system whereby an umbilical in use of the system is supported by said rollers around nearly half of its circumference. Thus with an umbilical handling system according to the present invention umbilicals have an increased support footprint (contact area) on the roller resulting in reduced fatigue levels, lower contact pressures with resultant lower levels of deformation and ovalisation. In addition to making use of the U shaped groove profile, the pressure applied to a given point on the umbilical at any time is also reduced by using a plurality, typically many, umbilical support rollers in the feed/recovery path. These spread the forces applied to the umbilical along its length and so reduce the deformation (ovalisation), thereby increasing the lifetime of the umbilical.

Preferably said support structure for supporting said plurality of umbilical support rollers defines an arcuate path along which an umbilical may be fed/recovered. Said rollers may be fixed to said support structure though preferably they are mounted on bearings which allows the rollers to rotate. Desirably said rollers are formed and arranged to be self aligning in the direction of travel of the umbilical in use of the handling system. The self aligning can be achieved by providing a bearing or axle along which a roller may move (sliding from ""side to side") as the umbilical passes through the U shaped groove. A typical umbilical is not straight (rectilinear) as it is unwound from a reel. The use of self aligning rollers avoids forcing the umbilical to conform exactly to a path as defined by rollers that are fixed or that rotate about bearings that allow no lateral movement. The self aligning rollers allow some "snaking" motion in the umbilical, avoiding additional stress to the umbilical as it is deployed or recovered.

Preferably said 'U' shaped groove profile is a semi-circle. Preferably said 'U' shaped groove profile has extended side flanges which extend above the 'IT shaped or semi-circular groove profile. Desirably the tops of said flanges are tapered from the outside of the roller towards the 'U' shaped groove profile so as to direct an umbilical in use of the handling system into the 'U' shaped groove profile of the roller.

Typically an umbilical of the type used in underwater applications will have a diameter of 60-120mm and thus preferably the 'U' shaped groove profile corresponds to that dimension though not in an interference fit. When an umbilical is being deployed or recovered the forces acting on it will tend to produce some ovaiisation as it passes over the umbilical support rollers. The dimensions of the 'U' shaped groove profile are therefore chosen so as to avoid catching or "pinching" the umbilical in the groove as the umbilical distorts under the anticipated forces.

Preferably the depth of the V shapedigroove is in the region of 60%— 80% of the diameter of an umbilical in use of the system. Preferably the rollers are manufactured from Nylon 6 (or 6/6, 6/12 or 12).

Brief Description of the Drawings

Further preferred features and advantages of the present invention will now be described with reference to the embodiments shown in figures 2-5. In the figures:

Figure 1 shows a prior art roller in use with an umbilical;

Figure 2 shows the umbilical feed recovery path defined by a support structure supporting a plurality of umbilical support rollers;

Figure 3 shows a front view of a roller;

Figure 4 is a side view of the roller supporting an umbilical; Figure 5 is a perspective view of the roller supporting an umbilical;

Figure 6 is a front view of another roller; and

Figure 7 shows a schematic view of an umbilical handling system.

Detailed Description of the Drawings

Figure 1 shows a conventional, prior art, roller 12 with a V shaped groove profile, supporting an umbilical 14 (shown in schematic cross section as a circle).

In more detail figure 2 shows schematically a support structure 10 comprising a frame base to which is fixedly mounted a roller support frame 11 which supports a series of rollers 12 which collectively define an umbilical feed/recovery path for supporting an umbilical 14. The support structure 10 forms part of an umbilical handling system (not shown further in this figure but see figure 7). As will be seen from figures 3-5 the rollers 12 have a 'U' shaped or semicircular groove profile 13, the dimensions of which conform to the cross-sectional profile and dimension of the umbilical 14 that is in use of the handling system and being supported by the rollers. As will be seen from the cross-sectional view shown in figure 3 the umbilical 14 sits within the semi-circular 'U' shaped groove profile such that it is supported by the roller around nearly half of its circumference thereby significantly increasing the footprint of support provided by the roller 2 to the umbilical 14. The rollers have upstanding side flanges which are tapered inwardly and which serve to guide an umbilical 14 into the groove 13.

The rollers are mounted on bearings 18 which have a degree of end float such that they are self-aligning with respect to the umbilical as it passes around the path defined by the support structure 10 and rollers 12. This self aligning feature is further illustrated in figure 6 which shows a roller 12 of the same form as in figures 3 to 5 but mounted on a bearing or axle 18a of longer length. As suggested by the double headed arrows 20 the roller 12 can move from side to side along the bearing 18a as the umbilical passes over it.

Figure 7 shows schematically an umbilical handling system. An umbilical 14 is wound on a hydraulic or air powered reel 22 that feeds the umbilical onto or from a feed/recovery path indicated by double headed arrows 24. The path 24 is defined by a support structure 10 that mounts a plurality of umbilical support rollers 12 having U shaped groove profiles.